As the price of petroleum continues to increase and as the availability of petroleum becomes more questionable, ethanol is becoming increasingly more important as a source of hydrocarbon-based fuels and chemicals. Ethanol has long been produced by the well known fermentation process. Another more recent process of producing ethanol is by the reaction of methanol with hydrogen and carbon monoxide (syn gas). This method has significant advantages because relatively inexpensive reactants are employed.
It has long been known that a water soluble cobalt catalyst will catalyze the reaction of methanol, hydrogen and carbon monoxide to produce ethanol. This cobalt-catalyzed reaction gives acceptable selectivity to ethanol, approximately 70 percent, but is plagued by poor methanol conversion of only about 50 percent. Practitioners of the art have attempted to increase the methanol conversion of this reaction by adding to the cobalt catalyst an iodide promoter; this has succeeded in increasing methanol conversion to over 90 percent but this increased activity results in a deleterious effect on ethanol selectivity, reducing it to about 25 percent and thereby severely limiting the ethanol yield. To overcome these problems, those skilled in the art have altered this catalyst system by the introduction of phosphorus compounds (U.S. Pat. No. 3,248,432) or by the addition of osmium or ruthenium halide promoters (U.S. Pat. No. 3,285,948). Unfortunately these catalyst systems are generally costly and cumbersome and in some cases relatively unstable, due to their complexity. It is interesting to note that both of these patents, U.S. Pat. No. 3,248,432 at column 1 lines 25-37 and U.S. Pat. No. 3,285,948 at column 1; lines 35-47 emphasize the poor selectivity to ethanol when the reaction is catalyzed by a system containing only cobalt and iodine. A process which can utilize the relatively simple cobalt-iodide catalyst system to produce ethanol from the reaction of methanol, hydrogen and carbon monoxide at high ethanol selectivity and at high methanol conversion would be of great advantage.